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By the end of this section, you will be able to:
  • Discuss the biogeochemical cycles of water, carbon, nitrogen, phosphorus, and sulfur
  • Explain how human activities have impacted these cycles and the potential consequences for Earth

Energy flows directionally through ecosystems, entering as sunlight (or inorganic molecules for chemoautotrophs) and leaving as heat during the many transfers between trophic levels. However, the matter that makes up living organisms is conserved and recycled. The six most common elements associated with organic molecules—carbon, nitrogen, hydrogen, oxygen, phosphorus, and sulfur—take a variety of chemical forms and may exist for long periods in the atmosphere, on land, in water, or beneath the Earth’s surface. Geologic processes, such as weathering, erosion, water drainage, and the subduction of the continental plates, all play a role in this recycling of materials. Because geology and chemistry have major roles in the study of this process, the recycling of inorganic matter between living organisms and their environment is called a biogeochemical cycle    .

Water contains hydrogen and oxygen, which is essential to all living processes. The hydrosphere    is the area of the Earth where water movement and storage occurs: as liquid water on the surface and beneath the surface or frozen (rivers, lakes, oceans, groundwater, polar ice caps, and glaciers), and as water vapor in the atmosphere. Carbon is found in all organic macromolecules and is an important constituent of fossil fuels. Nitrogen is a major component of our nucleic acids and proteins and is critical to human agriculture. Phosphorus, a major component of nucleic acid (along with nitrogen), is one of the main ingredients in artificial fertilizers used in agriculture and their associated environmental impacts on our surface water. Sulfur, critical to the 3–D folding of proteins (as in disulfide binding), is released into the atmosphere by the burning of fossil fuels, such as coal.

The cycling of these elements is interconnected. For example, the movement of water is critical for the leaching of nitrogen and phosphate into rivers, lakes, and oceans. Furthermore, the ocean itself is a major reservoir for carbon. Thus, mineral nutrients are cycled, either rapidly or slowly, through the entire biosphere, from one living organism to another, and between the biotic and abiotic world.

Head to this website to learn more about biogeochemical cycles.

The water (hydrologic) cycle

Water is the basis of all living processes. The human body is more than 1/2 water and human cells are more than 70 percent water. Thus, most land animals need a supply of fresh water to survive. However, when examining the stores of water on Earth, 97.5 percent of it is non-potable salt water ( [link] ). Of the remaining water, 99 percent is locked underground as water or as ice. Thus, less than 1 percent of fresh water is easily accessible from lakes and rivers. Many living things, such as plants, animals, and fungi, are dependent on the small amount of fresh surface water supply, a lack of which can have massive effects on ecosystem dynamics. Humans, of course, have developed technologies to increase water availability, such as digging wells to harvest groundwater, storing rainwater, and using desalination to obtain drinkable water from the ocean. Although this pursuit of drinkable water has been ongoing throughout human history, the supply of fresh water is still a major issue in modern times.

Questions & Answers

what is cell?
V.S.Nikhil Reply
The smallest structure and functional unit
vinod
Hydra reproduce through which process
Saint Reply
which is smallest organ in our body
Techi
pineal gland
Himangshu
Yh in the ears...
Mozua
why you hand plam is sweating in everytime
Techi
who is the father of mycology
Sagar Reply
Heinrich Anton de Bary
Delissa
describe the similarities and differences between cytokinesis mechanism found in animal cells versus in plant cells
hiro Reply
are humans beings considered to have the eukaryotic cells
success Reply
yes.....
Delissa
eukaryotes are organisms that possess cells with a nucleus enclosed in a membrane, humans, and all complex organisms are eukaryotes.
Delissa
so humans and animals also have cell membranes.... cause I did this test prep and they said plants...I just want to be sure
success
and thank you for your reply it was helpful👍✌
success
eu= "perfect", "good", karyon= nut, amound, nucleus
Tiago
you're welcome. Plants are also eukaryotes.
Delissa
plants, like animals, possess a nucleus bound by a membrane.
Delissa
similarities and differences between cytokinesis mechanism found in animal cell vs cell division
Raymark Reply
what is the name of a male flower?
Ikeomu Reply
staminate means flower containing only stamen
Falak
what is the definition of evolution in a population?
Homero Reply
the slow changing of a species to adapt to any changes in the environment or how it feeds/hunts. im not good at explaining things lol.
Eclipse
the organ which is sensitive to light in euglena
Fatimah Reply
the organ which is sensitive to light in euglena is
Fatimah
all chlorophyll containing motile cells are sensitive to light
Himangshu
there is no more other chapter
Sandeep Reply
Give tow examples for nutritional deficiency Diseases-
Singampalli Reply
How does a plant cell look like
Sang Reply
in a sleepers form
David
what do you mean ? I could not understand
Gul
they have a regular shape and a large vacoule
Fatimah
I thought it looked like rectangle
Abrahán
a stage in mitosis wherein in spindle fibers begin to shorten to pu the sister chromatids away from each other towards the opposite ends of the cell
Earl Reply
a stage in interphase where chromosome s are duplicated
Earl
What is biodiversity
Sp Reply
Hmm
Hele
Name two secretions of Golgi apparatus
Daniel Reply

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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